1. Field of the Invention
This invention relates generally to sprinklers, such as water actuated impulse sprinklers, one of the type having a sprinkler head fixed to a tubular spindle which is rotatably journaled in a bearing sleeve. More particularly, the invention relates to novel improved upper and lower seals for such sprinklers for sealing the clearance space between the spindle and bearing sleeve against entrance of water, dirt, grit and the like.
2. Prior Art
Large areas are commonly watered with water actuated impulse sprinklers of the kind having a spring biased impulse oscillator rotatably mounted on the sprinkler head for oscillation of a deflection vane on the oscillator into and from the water stream or jet emerging from a discharge orifice in the head. Each time the oscillator vane swings by spring action into the path of the water jet, the latter strikes the vane and imparts a torgue to the vane for rotating the oscillator into the stream. The stream is then diverted by the scoop, thus imparting torque to the oscillator in the opposite direction. This back and forth oscillatory motion of the oscillator imparts periodic impulses to the sprinkler head for driving the head in rotation with an intermittent rotary motion.
Sprinklers of this type have a bearing sleeve which is threaded at its lower end for connection to a water supply riser or the like. A bearing bore extends axially through the bearing sleeve. Journaled in the bearing bore is a tubular spindle. The sprinkler head is fixed to the upper end of this spindle. As described above, this sprinkler head carries an impulse oscillator actuated by the water jet issuing from the sprinkler head orifice for driving the head and spindle in intermittent rotation.
This type of sprinkler presents two major operating problems to which the present invention is addressed. One of these problems stems from the fact that the outer spindle diameter is made slightly smaller than the diameter of the bearing sleeve bore to permit free rotation of the sprinkler head and spindle. Accordingly, these exists between the spindle and bearing sleeve a small annular clearance space. Water leakage through this space is prevented by a combination seal and thrust bearing on the lower end of the spindle and engaging an annular sealing and thrust face on the lower end of the sleeve about the spindle. Some sprinklers of the character described, such as simple residential lawn sprinklers, however, have no provision for sealing the upper end of the clearance space. While these simple sprinklers are satisfactory for home use, they are ill suited to field irrigation use and other similar large scale commercial uses for the reason that dirt and grit often enter the clearance space through its open upper end and cause marring of the spindle and bearing sleeve bearing surfaces, jamming of the spindle in the bearing sleeve, and other undesirable consequences.
For this reason, impulse sprinklers for such commercial uses are commonly equipped with upper seals as well as lower seals for sealing both the upper and lower ends of the clearance space between the spindle and bearing sleeve against entrance of water, dirt, grit and the like. U.S. Pat. No. 2,980,341, for example, discloses a dual impulse sprinkler with both upper and lower seals.
While the existing dual seal sprinklers alleviate the problem of dirt and grit entrance into the bearing clearance space, they present another problem. Thus, one type of upper seal for such sprinklers and that shown in the above patent comprises a seal ring which surrounds and engages a circumferential bearing surface on the upper end of the bearing sleeve and is urged axially by a spring into sealing contact with an annular sealing face on the sprinkler head. The spring also urges the spindle upwardly relative to the bearing sleeve to retain the sealing surfaces of the lower seal and thrust bearing in contact, thus to prevent entrance of dirt and grit between these surfaces and into the bearing clearance space as long as the spindle is not pressed down into the bearing sleeve by compressing the spring, the upper seal may continue to function properly. Even then, however, some dirt and grit may enter between the bearing sleeve and the seal ring, which is relatively unyieldable, and cause jamming of the ring or wearing of its sealing surface and that of the bearing sleeve.
On the other hand, if the spring is compressed, as often happens, the seal ring is forced to slide downwardly along the bearing sleeve. When this occurs, corrosion, dirt and grit on the sleeve often enters between the sleeve and ring, causing the ring to jam on the sleeve with the result that ring does not return to its proper position of sealing engagement with the sprinkler head sealing face when the downward force on the head and spindle is removed.
In another type of known upper seal for a dual seal impulse sprinkler, the upper seal ring engages the spindle and is spring biased downwardly into sealing contact with an upper sealing face on the bearing sleeve. The seal ring is grooved in its upper face to form an annular sealing lip which bears against the spindle. This lip is intended to wipe or scrape the spindle in the event the latter is pressed downwardly through the seal ring and bearing sleeve by compression of the upper seal spring, thus to prevent the ring from jamming on the spindle. However, the upper groove in the seal ring is exposed to being filled with dirt and grit which inhibits or prevents flexing of the seal ring lip and thus renders the ring prone to jamming in the spindle when the latter is released to return upwardly by spring pressure.
Another major problem encountered in the existing impulse sprinklers involves the lower seal and thrust bearing, as is well known to those versed in the art of these sprinklers, this lower seal and thrust bearing must provide a somewhat critical frictional resistance to rotation of the spindle relative to the bearing sleeve. If the lower seal friction is too small, the spindle will slip or rotate in the bearing sleeve when the impulse oscillator is swung by the water jet impact from the jet path to tension the oscillator torsion spring, thus causing improper operation of or totally incapacitating the impulse driving means. On the other hand, if the lower seal friction is too large, the impacts generated by the impulse oscillator are incapable of driving the sprinkler head in rotation.